package com.weblibrary.db;
        import java.lang.reflect.Field;
        import java.lang.reflect.InvocationTargetException;
        import java.lang.reflect.Method;
        import java.lang.reflect.Modifier;
        import java.lang.reflect.ParameterizedType;
        import java.lang.reflect.Type;

    /**
     * 反射的 Utils 函数集合
     * 提供访问私有变量, 获取泛型类型 Class, 提取集合中元素属性等 Utils 函数
     * @author Administrator
     *
     */
    public class ReflectionUtils {


        /**
         * 通过反射, 获得定义 Class 时声明的父类的泛型参数的类型
         * 如: public EmployeeDao extends BaseDao<Employee, String>
         * @param clazz
         * @param index
         * @return
         */
        @SuppressWarnings("unchecked")
        public static Class getSuperClassGenricType(Class clazz, int index){
            Type genType = clazz.getGenericSuperclass();

            if(!(genType instanceof ParameterizedType)){
                return Object.class;
            }

            Type [] params = ((ParameterizedType)genType).getActualTypeArguments();

            if(index >= params.length || index < 0){
                return Object.class;
            }

            if(!(params[index] instanceof Class)){
                return Object.class;
            }

            return (Class) params[index];
        }

        /**
         * 通过反射, 获得 Class 定义中声明的父类的泛型参数类型
         * 如: public EmployeeDao extends BaseDao<Employee, String>
         * @param <T>
         * @param clazz
         * @return
         */
        @SuppressWarnings("unchecked")
        public static<T> Class<T> getSuperGenericType(Class clazz){
            return getSuperClassGenricType(clazz, 0);
        }

        /**
         * 循环向上转型, 获取对象的 DeclaredMethod
         * @param object
         * @param methodName
         * @param parameterTypes
         * @return
         */
        public static Method getDeclaredMethod(Object object, String methodName, Class<?>[] parameterTypes){

            for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
                try {
                    //superClass.getMethod(methodName, parameterTypes);
                    return superClass.getDeclaredMethod(methodName, parameterTypes);
                } catch (NoSuchMethodException e) {
                    //Method 不在当前类定义, 继续向上转型
                }
                //..
            }

            return null;
        }

        /**
         * 使 filed 变为可访问
         * @param field
         */
        public static void makeAccessible(Field field){
            if(!Modifier.isPublic(field.getModifiers())){
                field.setAccessible(true);
            }
        }

        /**
         * 循环向上转型, 获取对象的 DeclaredField
         * @param object
         * @param filedName
         * @return
         */
        public static Field getDeclaredField(Object object, String filedName){

            for(Class<?> superClass = object.getClass(); superClass != Object.class; superClass = superClass.getSuperclass()){
                try {
                    return superClass.getDeclaredField(filedName);
                } catch (NoSuchFieldException e) {
                    //Field 不在当前类定义, 继续向上转型
                }
            }
            return null;
        }

        /**
         * 直接调用对象方法, 而忽略修饰符(private, protected)
         * @param object
         * @param methodName
         * @param parameterTypes
         * @param parameters
         * @return
         * @throws InvocationTargetException
         * @throws IllegalArgumentException
         */
        public static Object invokeMethod(Object object, String methodName, Class<?> [] parameterTypes,
                                          Object [] parameters) throws InvocationTargetException{

            Method method = getDeclaredMethod(object, methodName, parameterTypes);

            if(method == null){
                throw new IllegalArgumentException("Could not find method [" + methodName + "] on target [" + object + "]");
            }

            method.setAccessible(true);

            try {
                return method.invoke(object, parameters);
            } catch(IllegalAccessException e) {
                System.out.println("不可能抛出的异常");
            }

            return null;
        }

        /**
         * 直接设置对象属性值, 忽略 private/protected 修饰符, 也不经过 setter
         * @param object
         * @param fieldName
         * @param value
         */
        public static void setFieldValue(Object object, String fieldName, Object value){
            Field field = getDeclaredField(object, fieldName);

            if (field == null)
                throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");

            makeAccessible(field);

            try {
                field.set(object, value);
            } catch (IllegalAccessException e) {
                System.out.println("不可能抛出的异常");
            }
        }

        /**
         * 直接读取对象的属性值, 忽略 private/protected 修饰符, 也不经过 getter
         * @param object
         * @param fieldName
         * @return
         */
        public static Object getFieldValue(Object object, String fieldName){
            Field field = getDeclaredField(object, fieldName);

            if (field == null)
                throw new IllegalArgumentException("Could not find field [" + fieldName + "] on target [" + object + "]");

            makeAccessible(field);

            Object result = null;

            try {
                result = field.get(object);
            } catch (IllegalAccessException e) {
                System.out.println("不可能抛出的异常");
            }

            return result;
        }
    }